import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.locks.Condition;

public class listTest {
    public static void main(String[] args) {
        List<Integer> ArrayList = new ArrayList<>(5);
        //转化为线程安全的
        List<Integer> list = Collections.synchronizedList(ArrayList);
        //写时复制
        CopyOnWriteArrayList list1 = new CopyOnWriteArrayList();
        Hashtable
    }
}
